As I said in my first comment I am only guessing, so I understand my opinion does not much matter to anyone but myself. Like I said while I lived in NC we had a couple fish kills, they were always reported as some type of mullet. Could there have been other fish involved just not in as great of number? Sure. The river was full of many types of fish (bass, catfish, crappie, brim, perch, and carp) but the news just reported about the mullet. So the fish kill doesn’t seem too far out in right field for me.
I have limited access to TV News (only get AFN) and pretty slow internet but from the few articles/shows I have seen the AR/LA bird kills were redwing black birds.
I would still think that if that incident was caused by some sort of release from the plant that you would see similar symptoms/results in other animals. I am obviously no expert in this field so it is all just my opinion.